In general, mortar or concrete using cement requires excellent strength and water permeability. A number of various researches have been carried out to prepare mortar or concrete having excellent physical properties in strength, water permeability, etc. For this purpose, many researches have been continued both in the field of cement and in the field of other mixing components used with the cement. As one of the mixing components, silica fume has been developed to prepare mortar or concrete having excellent physical properties in strength, water permeability, etc. when it is used with cement. However, the silica fume is very expensive and cannot be widely used at present.
Accordingly, the present inventors have developed an activated kaolin powder compound for using with cement so that the mortar or concrete prepared from the composition of cement and the activated kaolin powder shows good properties in strength and water permeability. The kaolin is naturally buried under the ground and can be obtained in a much lower cost than the silica fume.